Troubleshooting Warp in Postformed Laminate Countertops

Without balanced lamination (top and bottom side), tops are prone to warpage. April 18, 2010

We have been having issues on our postform line with countertops warping afterwards. I am looking for suggestions to prevent this. A backing laminate is the obvious fix, but will cost too much.

We are in a non-climate controlled building. Strategies to consider would include a light finish spray on the particleboard core's underside just before the contact is sprayed on top, some sort of paper or melamine backer, or heating the bottom of the core (just as we do to the surface of the glued laminate and particleboard). Anyone care to brainstorm?

Forum Responses
(Laminate and Solid Surface Forum)
From contributor J:
Not an expert on this, but you asked for brainstorming... Is the warp consistent, i.e. are all the problem tops cupping in the same direction? When does the warp become evident -immediately after manufacture, or only after they've left your facility? Where are you located/what's the climate inside the building like - dry or humid, hot or cold? How long are the substrates typically stored in this environment before use?

From contributor T:
The only way to properly correct the problem is just as you mentioned - balanced construction. Without it, you just roll the dice and wait until failure occurs. I could never understand why postform manufacturers don't follow the basic rules. Every postform top I have ever seen has a curl in it as the face laminate eventual pulls and cups the top. Most people just put up with it and try to pull it out with screws when installing. You say the right way costs too much, but that does not prevent you from producing an inferior product that will cause the end user issues for sure. Amazing!

From contributor B:
Being an old postformer I can tell you the only way I have ever found to help alleviate the problem is with backer. In truth, any hydroscopic (wood) core will move. The core is absorbing moisture or drying out (depending on conditions) while the laminate is holding one side tight. It's going to cup. I've tried stacking tops flat and on end, but it doesn't matter. You have to balance the construction of the core. It's cheaper in the long run to apply backing sheet than to fix warped tops. Any type of phenolic backing sheet is better than nothing - it doesn't have to be full thickness laminate or resanded backer. Gator-ply makes a paper backer that is okay for this use. Spraying the bottom with any type of sealer or paint won't solve it.

From contributor E:
I'm always amazed that countertops go out with HPL on one side. However, now that I'm in that industry I realize that it is totally cost driven. Some manufacturers offer backer for customers who require it, but most people don't want to pay the additional money for it, or they don't know about it, or can't tell the difference once it's installed. Either way, I agree that coating the bottom is not the answer. Applying a thin barrier product to the bottom is the only real way to keep moisture out and to stop, or at least moderate, the movement of the top.